The entry, 366 KB in PDF format, is named 2SK161 and, despite its schematic label, should contain the datasheet for that JIS-coded component. A 2SK number marks an N-channel field-effect transistor. Useful content for the bench includes the pin layout, package dimensions and maximum ratings, which guide replacement and substitution choices. Before soldering, compare the full marking and any suffix on the failed device with the document, and verify the footprint and pin order of any alternative part.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.